Partial characterization of human ileal alkaline phosphatase: differences between human ileal and duodenal enzymes

Properties of human ileal and duodenal alkaline phosphatase (ALP) were compared. The pH optimum, Km values, heat stability, inhibition of activity by amino acids, and antigenicity of ileal and duodenal ALPs were similar. Affinity for DEAE and Tyraminyl derivatives/Sepharose chromatographies, substrate specificity, molecular mass, isoelectric point, and sugar chain structure differed, suggesting two forms of intestinal enzyme. The N-terminal amino acid sequence, or peptide mapping or both suggest that the two major intestinal ALPs are identical, but the minor ALP may be differed from the sequence of major one.